Linearly polarized active artificial magnetic conductor

Abstract

An active artificial magnetic conductor comprising an array of unit cells, each unit cell comprising an electrically conductive patch that is connected with an electrically conductive patch of neighboring unit cell in a column of unit cells using a non-Foster negative inductor and having RF isolating plates or walls between rows of unit cells. These isolating plates or walls eliminate undesirable cross coupling between the non-Foster negative inductors. The electrically conductive patches may be formed by metallic patches preferably arranged in the 2D array of such patches. Each patch preferably has a rectilinear shape.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62 / 051,778, filed Sep. 17, 2014 and entitled “Linearly polarized active artificial magnetic conductor”, the disclosure of which is hereby incorporated herein by reference.[0002]This application is related to (i) U.S. Pat. No. 8,976,077 issued Mar. 10, 2015 and entitled “Wideband Tunable Impedance Surfaces” and also to (ii) U.S. Pat. No. 8,988,173 issued Mar. 24, 2015 and entitled “Differential Negative Impedance Converters and Inverters with Tunable Conversion Ratios”, the disclosures of which are also incorporated herein by reference.TECHNICAL FIELD[0003]This invention relates an active artificial magnetic conductor (AAMC) which includes a periodic array of unit cells which reflects electromagnetic waves incident on its surface with zero-degree phase shift.BACKGROUND[0004]It is often desirable to place antennas near and parallel to metallic surfaces. Howe...

AI Technical Summary

Benefits of technology

The present invention introduces an active artificial magnetic conductor that features a structure consisting of metallic patches arranged in a two-dimensional array. These patches have impedance elements that are connected to neighboring elements with non-Foster negative inductors. The structure also includes RF isolating plates between rows of unit cells to prevent cross coupling between the inductors. The impedance elements create an impedance to an incoming wave, which is represented by the grid admittance Yg. The technical effects of this invention include improved RF shielding, reduced interference, and improved magnetic conductivity.

Problems solved by technology

However these surfaces reflect electromagnetic waves out of phase with the incident wave, thus short circuiting the antennas.

But such AMCs have limited bandwidth.

At VHF-UHF frequencies, the thickness and / or permeability necessary for reasonable AMC bandwidth is excessively large for antenna ground-plane applications.

In U.S. Pat. No. 8,976,077 issued Mar. 10, 2015 and entitled “Wideband Tunable Impedance Surfaces”, a method of making an AAMC is described using Non-Foster Circuits (NFCs), but it does not disclose how to ensure stability of the AAMC itself which is due to the fact that it was discovered later that NFCs (which were designed with stability in mind) used in the AAMC resulted in instability due to cross coupling in the E-plane.

This instability is manifested as an uncontrolled oscillation of the NFCs and spurious emitted radiation.

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